In recent years the alloy, mercury cadmium telluride Hg.sub.1-x Cd.sub.x Te has been recognized as the most important material for mid-and long-wavelength infrared application. In the publication, in "J. Vac Sci Technol A6(4)", July/August 1988--the article entitled "Mercury cadmium telluride junctions grown in situ by molecular-beam epitaxy"--pp. 2623-26 n-isotype mercury cadmium telluride heterojunctions were made in situ by molecular beam epitaxy. The cadmium composition of both sides were doped with indium. In the "Concluding" paragraph of the publication, the statement is made that "The control of doping is also a very difficult task to achieve in this II-VI ternary alloy."